The present invention relates to a magnetic alloy, a magnetic recording medium and a method of producing the same, a target, and a magnetic recording device and, more particularly, to a magnetic alloy which has a high normalized coercive force, suppresses thermal agitation and also has thermally stable magnetic characteristics, a magnetic recording medium and a method of producing the same, a target for forming a magnetic film, and a magnetic recording device comprising the magnetic recording medium. The magnetic alloy and magnetic recording medium of the present invention are suited for use as hard disks, floppy disks, and magnetic tapes.
Although magnetic recording media have widely been employed as recording media having high density and large capacity in hard disk devices, recently, an improvement of recording/reproduction characteristics has been required to increase the recording density.
FIG. 19 and FIG. 20 are schematic views showing a hard disk as an example of a magnetic recording medium. FIG. 19 is a perspective view showing the whole body of a disk type magnetic recording medium, while FIG. 20 is a cross-sectional view taken along lines A-Axe2x80x2 of the magnetic recording medium shown in FIG. 19.
The magnetic recording medium 50 shown in FIG. 19 is composed of a substrate 51 made of a disk type non-magnetic substance, and an underlayer 54, a recording layer 55 and a protective layer 56, which are formed on the substrate 51.
In the magnetic recording medium 50 of this example, for example, a substrate comprising a base 52 made of an Al alloy, and a non-magnetic layer 53 made of Nixe2x80x94P provided on the surface of the base 52 is used as the substrate 51 made of the non-magnetic substance. As the substrate 51, a base made of glass is sometimes used. On the substrate 51, an underlayer 54 made of Cr, a recording layer 55 made of a magnetic film of CoCrTa or CoCrTaPt, and a protective layer 56 made of C (carbon) are laminated in order. The protective film 56 is sometimes coated with a lubricating film made of a fluororesin such as perfluoropolyether. In the cross-sectional structure shown in FIG. 20, a lubricating film is omitted.
With respect to the magnetic film, which constitutes the recording layer 55 in this kind of magnetic recording medium 50, a magnetic film made of a CoNiCr alloy (having Hc of about 1200 Oe) has been used in first generation magnetic recording media and a magnetic film made of a CoCrTa alloy with a composition which is close to Co84-86Cr10-12Ta4 has been used in second generation magnetic recording media and, furthermore, a magnetic film (having an Hc of about 1800 Oe) made of a CoCrTa alloy with a composition close to Co78-80Cr15-17Ta5 has been used in third generation magnetic recording media and a magnetic film made of a CoCrTaPt alloy with a composition close to Co54-77Cr16-22Ta2-4Pt5-10 has been used in fourth generation magnetic recording media.
These changes in generations were caused by the requirements for more excellent magnetic characteristics for the magnetic film to be used in keeping with improvements in the recording density of magnetic recording media, resulted in the development of various materials.
By the way, the present inventors had already learned that, even if a magnetic film made of an alloy having the above magnetic characteristics is formed on a substrate, only a coercive force which is drastically smaller than the coercive force that the film should ideally exhibit, is obtained in the magnetic film. For example, it can be surmised that the coercive force of about 3000 Oe of an isotropic medium can; be exhibited by a CoNiCr alloy and a coercive force of about 2500 Oe can be exhibited by a CoCrTa alloy. However, it is considered that a magnetic films having a coercive force which is far smaller than the above values are sometimes obtained in magnetic films made of these alloy materials obtained by a general film forming process and only a magnetic film having a half or less of the ideal coercive force are obtained in some cases.
Therefore, the present inventors have intensively studied intensively methods of producing magnetic films made of CoCrTa and CoCrTaPt alloys, which are exclusively used at present, in order to cope with the increase of the recording density of magnetic recording media and found a method capable of significantly improving the magnetic characteristics of these magnetic films. They termed this method an ultra clean process and various patent applications were filed (see U.S. Pat. No. 5,853,847 and National Application PCT/JP94/01184). According to the technology of the above patent, it is made possible to obtain a CoNiCr magnetic film or a CoCrTa magnetic film having a high coercive force within a range from 2700 to 3000 Oe by purifying the film forming atmosphere and control the ultimate vacuum degree to 3xc3x9710xe2x88x929 Torr (400xc3x9710xe2x88x929 Pa) or less and by dry-eyching using an Ar gas containing about 1 ppb of impurities such as H2O, the surface of the substrate, on which an underlayer of Cr is formed, to remove impurities such as oxides from the surface of the substrate. This kind of a magnetic film obtained by general film forming processes usually exhibits a coercive force within a range from about 1500 to 2000 Oe.
However, considerable progress has been made in magnetic recording media and it is required to develop a more excellent magnetic film in place of the CoCrTa alloy magnetic film or CoCrTaPt alloy magnetic film. It is also required to develop a magnetic film which exhibits excellent magnetic characteristics under general film forming conditions without using the above ultra clean process.
An object of the present invention is to provide a magnetic alloy which has a high normalized coercive force, suppresses thermal agitation and also has thermally stable magnetic characteristics, or a magnetic recording medium comprising a magnetic film made of the alloy.
Another object of the present invention is to provide a method of producing a magnetic recording medium having the above characteristics.
Still another object of the present invention is to provide a target suited for use in the production of a magnetic recording media having the above characteristics.
Yet another object of the present invention is to provide a magnetic recording device comprising a magnetic recording medium having the above excellent characteristics.
The magnetic alloy of the present invention is a magnetic alloy consisting essentially of cobalt (Co), chromium (Cr) and germanium (Ge), the composition of said magnetic alloy being represented by the general formula:
CoxCryGez
where x, y and z, which represent the composition ratio, satisfy the relationships: 78xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, and x+y+z=100 (provided that x, y, and z represent the composition ratio in terms of atomic %).
According to the magnetic alloy with the above composition, it is possible to obtain a magnetic alloy which has magnetic characteristics capable of accommodating increases in recording density, i.e. both a high normalized coercive force and magnetocrystalline anisotropy, and also has a more excellent magnetic anisotropy field.
In the present invention, the composition ratio can preferably satisfy the relationships: 82xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, and 2.5xe2x89xa6zxe2x89xa614.
With a composition within the above range, the relationship 4xcfx80Ms/Hkgrainxe2x89xa61.0, which is the condition required to obtain a high normalized coercive fore(Hc/Hkgrain) of 0.35 or more, is secured to obtain a magnetocrystalline anisotropy (Kugrain) of 1.5xc3x97106 erg/cm3 or more, thus making it possible to form a magnetic alloy which also has thermally stable magnetic characteristics.
The magnetic alloy of the present invention is a magnetic alloy consisting essentially of cobalt (Co), chromium (Cr), germanium (Ge), and an element T (T represents one or more of the elements of Ta, Si, Nb, B, Ni, and Pt), the composition of said magnetic alloy being represented by the general formula:
(CoxCryGez)100xe2x88x92cTc
where x, y, z, and c, which represent the composition ratio, satisfy the relationships: 60xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, cxe2x89xa620, and x+y+z=100 (provided that x, y, z, and c represent a composition ratio in terms of atomic %).
In the magnetic alloy of the present invention, the composition ratio can satisfy the relationships: 60xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, and 2.5xe2x89xa6zxe2x89xa614.
In the magnetic alloy of the present invention, c, which represents the composition ratio of said element T, can be controlled to 5 atomic % or less if said element T represents one or more elements of Ta, Si and Nb, and c, which represents a composition ratio of said element T, can be controlled to 9 atomic % or less in case said element T is B.
The magnetic alloy of the present invention is a magnetic alloy consisting essentially of cobalt (Co), chromium (Cr), germanium (Ge), platinum (Pt), and an element Txe2x80x2 (Txe2x80x2 represents one or more elements of Ta and B), the composition of said magnetic alloy being represented by the general formula:
(CoxCryGezPtv)100xe2x88x92cxe2x80x2Txe2x80x2cxe2x80x2
where x, y, z, v, and cxe2x80x2, which represent the composition ratio, satisfy the relationships: 45xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, 2xe2x89xa6vxe2x89xa625, and 1xe2x89xa6cxe2x80x2xe2x89xa612 (provided that x, y, z, v and cxe2x80x2 represent a composition ratio in terms of atomic %).
According to the magnetic alloy of these compositions, it is easy to obtain a low medium noise, a high signal output and an excellent S/N ratio, in addition to excellent magnetic characteristics of the CoCrGe ternary alloy described above.
In the magnetic alloy of the present invention, c, which represents the composition ratio of B, can be controlled to 1 atomic % or more and 8 atomic % or less if said Txe2x80x2 is B.
In the magnetic alloy of the present invention, c, which represents the composition ratio of Ta, can be controlled to 1 atomic % or more and 8 atomic % or less in case said Txe2x80x2 is Ta.
With compositions within the above range, it is possible to securely obtain a low medium noise, a high signal output and an excellent S/N ratio, in addition to excellent magnetic characteristics of the CoCrGe ternary alloy described above.
The present invention is characterized by a magnetic recording medium comprising a substrate and a ferromagnetic metal magnetic film formed on said substrate via a metallic underlayer, said ferromagnetic metal magnetic film being a magnetic film made of a ternary alloy consisting of cobalt (Co), chromium (Cr), and germanium (Ge), an alloy composition of said ferromagnetic metal magnetic film being represented by the general formula:
CoxCryGez
where x, y and z, which represent a composition ratio, satisfy the relationships: 60xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, and x+y+z=100 (provided that x, y and z represent a composition ratio in terms of atomic %).
According to the ferromagnetic metal magnetic film of a magnetic alloy with the above composition, it is possible to obtain a magnetic recording medium which has magnetic characteristics capable of accommodating increases in the recording density, i.e. both a high normalized coercive force and magnetocrystalline anisotropy, even when using a conventional film forming process utilizing a film forming chamber, the ultimate vacuum degree of which is on the order of 10xe2x88x926 Torr.
In the magnetic recording medium of the present invention, the composition ratio of said ferromagnetic metal magnetic film can satisfy the relationships: 82xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, and 2.5xe2x89xa6zxe2x89xa614.
With a composition within the above range, the relationship 4xcfx80Ms/Hkgrainxe2x89xa61.0, which is the condition required to obtain a high normalized coercive force (Hc/Hkgrain) of 0.35 or more, is secured to obtain a ferromagnetic metal magnetic film having a magnetocrystalline anisotropy (Kugrain) of 1.5xc3x97106 erg/cm3 or more, thus making it possible to form a magnetic recording medium which also has thermally stable magnetic characteristics.
The present invention is characterized by a magnetic recording medium comprising a substrate and a ferromagnetic metal magnetic film formed on said substrate via a metallic underlayer, said ferromagnetic metal magnetic film being a magnetic film consisting essentially of cobalt (Co), chromium (Cr), germanium (Ge), and an element T (T represents one or more of the elements Ta, Si, Nb, B, Ni, and Pt), the composition of said magnetic alloy being represented by the general formula:
(CoxCryGez)100xe2x88x92cTc
where x, y, z, and c, which represent the composition ratio, satisfy the relationships: 60xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, cxe2x89xa620, and x+y+z=100 (provided that x, y and z represent the composition ratio in terms of atomic %).
In the present invention, the composition ratio of said ferromagnetic metal magnetic film can satisfy the relationships: 73xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, and 2.5xe2x89xa6zxe2x89xa614.
In the present invention, c, which represents the composition ratio of said element T, can be controlled to 5 atomic % or less if said element T represents one or more of the elements Ta, Si and Nb, and c, which represents the composition ratio of said element T, can be controlled to 9 atomic % or less in case said element T is B.
The present invention is characterized by a magnetic recording medium comprising a substrate and a ferromagnetic metal magnetic film formed on said substrate via a metallic underlayer, said ferromagnetic metal magnetic film being a magnetic film consisting essentially of cobalt (Co), chromium (Cr), germanium (Ge), platinum (Pt), and an element Txe2x80x2 (Txe2x80x2 represents one or more of the elements Ta and B), the composition of said magnetic alloy being represented by the general formula:
(CoxCryGezPtv)100xe2x88x92cxe2x80x2Txe2x80x2cxe2x80x2
where x, y, z, v, and cxe2x80x2, which represent the composition ratio, satisfy the relationships: 45xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, 2xe2x89xa6vxe2x89xa625, and 1xe2x89xa6cxe2x80x2xe2x89xa612 (provided that x, y, z, v, and cxe2x80x2 represent the composition ratio in terms of atomic %).
According to the ferromagnetic metal magnetic film of these compositions, it is easy to obtain a low medium noise, a high signal output and an excellent S/N ratio, in addition to excellent magnetic characteristics of the CoCrGe ternary alloy described above.
In the present invention, cxe2x80x2, which represents the composition ratio of B, can be controlled to 1 atomic % or more and 8 atomic % or less in case said Txe2x80x2 is B.
In the present invention, cxe2x80x2, which represents the composition ratio of Ta, can be controlled to 1 atomic % or more and 8 atomic % or less in case said Txe2x80x2 is Ta.
With a composition within the above range, it is made possible to securely obtain a low medium noise, a high signal output and an excellent S/N ratio, in addition to excellent magnetic characteristics of the CoCrGe ternary alloy described above.
The present invention is characterized by forming at least a ferromagnetic metal magnetic film on a metallic underlayer using any of the sputtering, vacuum deposition, CVD, ion beam, or laser deposition film forming methods in the production of the magnetic recording medium described above.
By carrying out this film forming method, it is made possible to obtain the desired magnetic recording medium comprising a substrate and a ferromagnetic metal magnetic film having excellent magnetic characteristics formed on the substrate.
In the present invention, a film can be formed in a non-bias state where an electrical bias is not applied to a substrate in case of forming at least a ferromagnetic metal magnetic film on a metallic underlayer in the production of the magnetic recording medium described above.
According to the magnetic recording medium comprising the above CoCrGe ternary alloy magnetic film having a specific composition ratio or the CoCrGeT or CoCrGeTxe2x80x2 alloy magnetic film having the above specific composition, a film can be formed in a non-bias state without applying a bias to a substrate so that an insulating glass having excellent evenness can be employed as the substrate. Furthermore, the magnetic recording medium has the feature defects due to application of the bias to the substrate during production can be prevented, thereby making stable production possible to.
In the present invention, the above ferromagnetic metal magnetic film can be formed on a substrate by means of sputtering using at least a composite target comprising Cr chips and Ge chips placed thereon in case of carrying out the method described above.
The present invention is characterized by disposing a substrate in a film forming chamber, forming a metallic underlayer on said substrate using a target for forming an underlayer provided in said film forming chamber, and forming a ferromagnetic metal magnetic film on said metallic underlayer in said film forming chamber using a target for forming a ferromagnetic metal magnetic film disposed in the film forming layer after forming the metallic underlayer in case of carrying out the method described above.
The present invention is characterized by a target for forming a magnetic film, consisting essentially of cobalt (Co), chromium (Cr) and germanium (Ge), the composition of said target being represented by the general formula:
CoxCryGez
where x, y and z, which represent the composition ratio, satisfy the relationships: 78xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, and x+y+z=100 (provided that x, y, and z represent the composition ratio in terms of atomic %).
The present invention is characterized in that said composition ratio satisfies the relationships: 82xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, 2.5xe2x89xa6zxe2x89xa614, and x+y+z=100.
The present invention is characterized by a target for forming a magnetic film, consisting essentially of cobalt (Co), chromium (Cr), germanium (Ge), and an element T (T represents one or more of the elements Ta, Si, Nb, B, Ni and Pt), the composition of said target being represented by the general formula:
(CoxCryGez)100xe2x88x92cTc
where x, y, z and c, which represent the composition ratio, satisfy the relationships: 60xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, cxe2x89xa620, and x+y+z=100 (provided that x, y, z, and c represent the composition ratio in terms of atomic %).
Using a target with such a composition, a ferromagnetic metal magnetic film having excellent magnetic characteristics with the composition described above can be obtained by means of a film forming method such as sputtering.
In the present invention, said composition ratio can preferably satisfy the relationships: 73xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, and 2.5xe2x89xa6zxe2x89xa614.
According to the target with such a composition within the above range, the relationship 4xcfx80Ms/Hkgrainxe2x89xa61.0, which is the condition required to obtain a high normalized coercive force (Hc/Hkgrain) of 0.35 or more, is secured, thus making it possible to form a magnetic recording medium comprising a ferromagnetic metal magnetic film, which has a magnetocrystalline anisotropy (Kugrain) of 1.5xc3x97106 erg/cm3 and also has thermally stable magnetic characteristics.
The present invention may be characterized in that c, which represents the composition ratio of said element T, is 5 atomic % or less if said element T represents one or more of the elements Ta, Si and Nb, and c, which represents the composition ratio said element T, is 9 atomic % or less if said element T is B.
The target of the present invention may be characterized by a target for forming a magnetic film, consisting essentially of cobalt (Co), chromium (Cr), germanium (Ge), and an element Txe2x80x2 (Txe2x80x2 represents one or more of the elements Ta and B), the composition of said target being represented by the general formula:
(CoxCryGezPtv)100xe2x88x92cxe2x80x2Txe2x80x2cxe2x80x2
where x, y, z, v, and cxe2x80x2, which represent the composition ratio, satisfy the relationships: 45xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa625, 2xe2x89xa6zxe2x89xa615, 2xe2x89xa6vxe2x89xa625, and 1xe2x89xa6cxe2x80x2xe2x89xa612 (provided that x, y, z, v, and cxe2x80x2 represent the composition ratio in terms of atomic %).
The target may also have a composition ratio satisfying the relationships: 82xe2x89xa6xxe2x89xa687, 2.5xe2x89xa6yxe2x89xa613, and 2.5xe2x89xa6zxe2x89xa614.
It may also be a target, wherein c, which represents a composition ratio of B, is 1 atomic % or more and 8 atomic % or less in case said Txe2x80x2 is B.
The target may also have a value of c, which represents the composition ratio of Ta, of 1 atomic % or more and 8 atomic % or less if said Txe2x80x2 is Ta.
According to a target with a composition within the above range, the relationship 4xcfx80Ms/Hkgrainxe2x89xa61.0, which is the condition required to obtain a high normalized coercive force (Hc/Hkgrain) of 0.35 or more, is secured, thus making it possible to form a magnetic recording medium comprising a ferromagnetic metal magnetic film which has magnetocrystalline anisotropy (Kugrain) of 1.5xc3x97106 erg/cm3 and also has thermally stable magnetic characteristics.
The magnetic recording device of the present invention is characterized by comprising the above magnetic recording medium, a driving section for driving said magnetic recording medium, a magnetic head, and a moving means for moving said magnetic head relatively to said magnetic recording medium.
Since the magnetic recording device comprises the above-described magnetic recording medium having excellent magnetic characteristics, it is possible to provide an excellent magnetic recording device which can accommodate increases of the recording density and has a great resistance to thermal agitation, and which also has a low medium noise and can enhance the signal output.
The magnetic recording device of the present invention is characterized in that the,reproduction section of said magnetic head consists of a magnetic resistance effect type magnetic element.
Since the magnetic head, a reproduction section of which consists of a magnetic resistance effect type magnetic element, accommodate the increases of the recording density of the magnetic recording medium and can also read fine magnetic information, it is possible to provide an excellent magnetic recording device which can accommodate increases of the recording density and has a great resistance to thermal agitation, and which also has a low medium noise and can enhance the signal output.